Streptococcal Invasive Disease - Group B, 2002

Three hundred eleven cases of Group B streptococcal invasive disease (6.3 per 100,000 population), including 24 deaths, were reported in 2002. These cases included those in which group B Streptococcus (GBS) was isolated from a normally sterile site, in addition to nine cases involving a miscarriage or stillbirth in which placenta was the site of disease.

Overall, 139 (45%) cases presented with bacteremia without another focus of infection. The other most common types of infection were cellulitis (16%), arthritis (9%), pneumonia (8%), osteomyelitis (4%), and meningitis (3%). The majority (78%) of cases had GBS isolated from blood only. Sixty percent of cases occurred among residents of the seven-county Twin Cities metropolitan area. Forty-seven (15%) case-patients were infants less than 1 year of age, and 153 (49%) were 60 years of age or older.

Forty-five cases of infant (early-onset or late-onset) or maternal GBS disease were reported, compared to 53 cases in 2001. Twenty-seven infants developed invasive disease within 6 days following birth (i.e., early-onset disease), and 18 infants became ill at 7 to 89 days of age (i.e., late-onset disease). Nine stillbirths or spontaneous abortions were associated with 15 maternal invasive GBS infections.

From 1997 to 2002, 1,666 cases of GBS invasive disease were reported; 1,282 (77%) of these cases were adult non-maternal, 169 (10%) were early onset, 114 (7%) were late-onset, 84 (5%) were maternal, and 17 (1%) were among children 90 days to 14 years of age. During this time period, 169 women had infants who developed early-onset GBS disease, and eight infants died. Thirty-one infants born at less than 37 weeks' gestation accounted for 18% of early-onset cases. Bacteremia without another focus of infection (83%) was the most common type of infection in these early-onset cases, followed by pneumonia (18%) and meningitis (7%).

In 1996, CDC, the American Academy of Pediatrics, and the American College of Obstetricians and Gynecologists released consensus guidelines urging prenatal care providers to use risk-based or screening-based approaches to prevent perinatal GBS disease. In light of these guidelines, MDH reviewed the maternal charts for 167 (99%) of 169 early-onset cases. Fifty (30%) women had prenatal screening for GBS; 16 (32%) were positive, 30 (60%) were negative, and four (8%) had an unknown result. Among those who were screened, 88% either did not receive screening for vaginal and rectal sites at greater than 34 weeks' gestation or did not have documentation of the site or date of screening. Overall, 15% of mothers of infants with invasive GBS disease received intrapartum antimicrobial prophylaxis (IAP). For women with risk factors and positive GBS cultures, regardless of site and date, 44% received IAP. Among women with risk factors and unknown or negative cultures, 32% received IAP; 56% of women with no risk factor and a GBS positive culture received IAP. These data indicate that not all women with indications for IAP are receiving the appropriate preventive therapy.

In August 2002, the Perinatal GBS Disease Prevention guidelines were revised. Key changes include the recommendation for universal prenatal screening of all pregnant women at 35 to 37 weeks' gestation, as well as updated prophylaxis regimens for women with penicillin allergies.

• For up to date information see: Group B Streptococcus (GBS)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2002